This project focuses on structural design, chemical synthesis, and modification of molecules important to reproductive and developmental biology. A. A peptide sequence in proteins, -Pro-Lys-Lys-Lys-Arg-Lys-Val-, known to lead to translocation into the nucleus, was synthesized as a N-trifluoroacetylateld sulfohydroxysuccinimido ester. After coupling to avidin and removal of trifluoracetyl groups by peperidine, a conjugate that has two peptide units linked through the COOH-terminal group of the peptide to two e-NH2-groups in the tetrameric avidin molecule was obtained. This conjugate exhibited full biotin-binding activity. Similarly, a peptide of 22 amino acid residues, designted as Differentiation Peptide B, was synethesized by a solid phase method and derivatized as NAlphaNe-trifluoroacetyl pentafluorophenyl ester, and then conjugated to bovine thyroiglobulin. In both cases, defined linkages between peptide and protein were achieved. B. Dimeric gonadotropin releasing hormone agonists and antagonists. Three dimeric des-Gly10-[D-Lys6]-GnRH-NHEt cross-linked at e-amino group with -Gly-n-COCH2CO-Gly-10-(D-Lys-6)n - (n=0, 1, 2) exhibited increased biological activities and mast cell histamine releasing activity oiver the monomer. However, a dimer (n=1) was found to display a substantial increase of a post-coital antifertility effect over the increase of histamine releasing side-effect. A similar approach was taken in the synthesis and purification of dimers of a GnRH antagonist of the following sequence: Ac-D-pC1Phe-D-pCLPhe-D-Trp-Ser-Tyr-D-Lys-Leu-Arg-Pro-D-Ala-NH2. Antisera against the agonist and the antagonist monomers were also generated. C. Determinations of amino acid compositions and partial amino acid sequence of induced NAD(P)H:menadione oxidoreductase allowed deduction of correct reading frame of the cloned cDNA.